1. Field of the Invention
The present invention concerns a device as well as a method for data transfer between two parts moving relative to one another while maintaining a slight distance between the parts.
2. Description of the Prior Art
A device of the above type is known that has a transmission device with at least one transmission antenna (connected with a transmitter) on one of the parts moving relative to one another and one receiver device that has at least one reception antenna (connected with a receiver) on the other of the parts moving relative to one another. The transmission antenna and/or the receiver antenna is/are fashioned and arranged as radio-frequency conductors, such that during at least one segment of the relative movement, signals submitted by the transmission antenna are received by the reception antenna by capacitive or inductive coupling.
The preferred application field of the present invention concerns data transfer between the rotating part and the stationary part of a computed tomography apparatus. In operation of the computed tomography apparatus the data acquired by the x-ray detectors must be transferred from the rotating part to the stationary part of the computed tomography apparatus in order to further process the data. The data quantity to be transferred increases with the continuous development of computed tomography systems.
In many presently available computed tomography apparatuses a slip ring system as known is, for example, from U.S. Pat. No. 5,140,696 or U.S. Pat. No. 5,530,422 is used for data transfer. This data transfer system has a transmission device on the rotating part as well as a reception device on the stationary part. The transmission device has at least one radio-frequency conductor connected with a transmitter and forming a transmission antenna that is arranged on the periphery of the rotating part of the rotating frame. The reception device has a receiver and at least one reception antenna connected with the receiver, this reception antenna being formed by a short segment of a radio-frequency conductor. In operation of the computed tomography apparatus, the transmission antenna moves past the reception antenna attached on the stationary part at a slight distance, such that the signals propagating on the transmitting radio-frequency conductor are capacitively launched or injected into the reception antenna via the developing wave. The radio-frequency conductors are normally fashioned as microstrip conductors in a PCB (printed circuit board) technique and can be realized cost-effectively.
This transfer technology, however, due to the steadily increasing data rate (already at multiple gigabits/s (Gbps)) in computed tomography systems, in particular in multi-line computed tomography systems, will lead to problems in the near future since the signals or data to be transferred must be conducted over a larger distance in the transmitting radio-frequency conductor dependent on the current position of the rotating frame. Given increased data rate, strong signal distortions that limit the transferable data rate arise in the data transfer due to frequency-dependent losses, in particular due to dielectric losses and the skin effect. Since a shortening of the radio-frequency conductor used in the transmission device is not possible in computed tomography systems, a higher data rate can be achieved only by the use of special low-loss dielectric materials in the radio-frequency conductor. Such materials are expensive and are not always available for the desired data rates.